Conventional packet-switching networks permit cheap and reliable communications independent of the distance between a source node and a destination node in the network. Conventional networks, however, rely upon either public keys or shared private keys to provide privacy for messages that pass through the network's links. Public keys have the drawback that they have never been proven to be difficult to decipher. Therefore, it is possible that an efficient means of cracking public keys may one day be discovered. The result of such a discovery would be that all public key technology would become obsolete. All supposedly “secure” networks based on public key technology would thus become vulnerable. Shared private keys also have the drawback that the logistics of distributing the private keys can be prohibitive.
Quantum cryptography represents a recent technological development that provides for the assured privacy of a communications link. Quantum cryptography is founded upon the laws of quantum physics and permits the detection of eavesdropping across a link. Quantum cryptography, thus, ensures the security of keys distributed across the link. Quantum cryptographic techniques have been conventionally applied across single links in a network. Quantum cryptography requires the reliable transmission and receipt of single photons for distributing encryption/decryption keys. However, single photons cannot be reliably transmitted over large distances. Single quantum cryptographic links are, therefore, distance limited. For example, a single quantum cryptographic link cannot be any longer than some tens of miles when transmitting through fiber optic cabling.
Therefore, there exists a need for a system and method that combines the assured privacy achieved with quantum cryptography with the distance independent communication achieved with conventional multi-node, multi-link packet switching networks.